Lovebox is London's annual urban disco. Leggings and leotards, in sundry neons, are practically compulsory this year, as are £4 cupcakes, sponsored photo booths and a million makeup stalls. All this corporate colour distracts from a less-than-vintage lineup, although Saturday and Sunday boast some impressive performances.

Saturday, unexpectedly, belongs to Kelis. In a black bustier and taffeta skirt, she sings – and drums – through a greatest hits set, driven by a salvo of pop's greatest hooks. She mashes up her hit single Milkshake with Madonna's Holiday and Cyndi Lauper's Girls Just Want to Have Fun, then slides into Nirvana's Smells Like Teen Spirit and Donna Summer's I Feel Love. These aren't new tricks, but she gives them a startlingly original glow.

Women rule elsewhere on Saturday, too. Pop trio Stooshe feel refreshingly rough around the edges, like a cartoon Bananarama. Emeli Sandé's Heaven soars across Victoria Park, as does her cover of Coldplay's Every Teardrop Is a Waterfall. Friendly Fires' headline set, however, proves tough to pull off. After a slow start, an extended Kiss of Life brings tropical shimmer to the showers.

Overwhelming ... Chic. Photograph: Rune Hellestad/Corbis

Sunday offers old-school disco proper. Newcomers Ronika and Tyson revive 1980s' synth sounds on the second stage, but when Chic arrive mid-afternoon, their originals are overwhelming. "We're not a covers band," says Nile Rodgers, "we did this shit in the first place." Here are Le Freak and Good Times – which Rodgers bleeds into Rappers' Delight, the pioneering hip-hop track that lifted its bassline – Sister Sledge's We Are Family and David Bowie's Let's Dance. It's a staggering CV.

Later, an even bigger crowd awaits Lana Del Rey. Famously inconsistent live, her vocals are strong tonight, as her trademark videos sigh nostalgically behind her. Gay men snog in droves to the gorgeous Blue Jeans and Summertime Sadness. Still, her charisma is pure Stepford Wife, as if her battery is about to die.

Disco diva ... Grace Jones. Photograph: Rune Hellestad/Corbis

Then comes Grace Jones. Last seen hula hooping at the Diamond Jubilee concert, she appears from inside a cape, wearing a hat resembling a vagina. "My mum's here today," she says later, just after simulating sex with the stage. "The apple doesn't fall far from the tree." As she wiggles her incredible buttocks throughout Pull Up to the Bumper, and drinks wine through a straw during La Vie en Rose, you boggle that a woman like this can be part of the establishment. Then you start dancing again: the power of disco indeed. Jude Rogers

Festival watch

Best actKelis, and her two-piece female band. Constant reminders of the great songs she has been involved with (Ol' Dirty Bastard's Got Your Money, Trick Me, Acapella), and brilliant lifts from Labrinth's Earthquake, Robyn S's Show Me Love, and Bomfunk MCs' Freestyler.